Integrated circuit driver devices typically include high voltage and low voltage regions and use at least three operating voltages. The different operating voltages are used for different device types formed on the substrate and the different operating voltages are associated with gate oxides thicknesses that differ according to the operating voltage. Devices formed in low voltage areas may include gate oxide thicknesses approximately 150 angstroms or less whereas in the high voltage areas formed on the same substrate, devices that operate at high voltages (greater than 15 volts) typically require gate oxide thicknesses above 300 angstroms.
A challenge in semiconductor manufacturing technology is to form multiple gate oxides of various thicknesses on the same substrate, then to define and form associated devices using the various gate oxides without attacking gate oxide integrity of the various thickness gate oxides. Wet etching procedures (also referred to as wet dips or strips) are typically used to remove gate oxide from areas that are not masked by a transistor gate or other device. Multiple wet etching procedures directed to removing the multiple gate oxides, or wet etching procedures directed to removing the thickest gate oxide, may result in gate oxide penetration and/or undercut. This leads to GOI (gate oxide integrity) failures and inoperative devices.
It would therefore be desirable to provide semiconductor integrated circuit devices such as driver devices that utilize multiple operating voltages and therefore include multiple gate oxide thicknesses, on the same substrate, using a processes that form devices with various gate oxides, without attacking or compromising the gate oxides.